456 COMPARATIVE MORPHOLOGY OF FUNGI 



and by way of an appendix, a still obscure family, the Hemigasteraceae, 

 angiocarpous forms without lamellae. The seventh and largest family, 

 that of the Agaricaceae, is entirely artificial and is mainly distinguished 

 by a lack of marked characteristics. The especially striking morpho- 

 logical relationships between the families are shown on page 455. 



Hygrophoraceae. — This family is connected with the Dictyolaceae 

 both in structure and character of the fructifications; the elevations 

 of the hymenophore are developed to true lamellae which rise freely, 

 comparatively far apart, and have broad cross-sections (Battaille, 1910). 

 They are alternately of different lengths; the longer ones are often 

 decurrent; the surface of the pileus is slimy and the trama fleshy or waxy. 

 As far as their ontogeny has been followed in detail, in Hygrophorus 

 (Hygrocybe) miniatus, H. (Hygrocybe) nitidus, H. (Camarophyllus) borealis 

 (Douglas, 1918), H. (Limacium) Karsteni, H. (Limacium) agathosmus, 

 H. Langei (H. {Hygrocybe) constans) and H. (Hygrocybe) nigrescens 

 (Kuehner, 1926), in the young fructification the lamellae develop 

 exogenously in the annular furrow beneath the pileus fundament and 

 centrifugally from the stipe. In the other species, H. (Limacium) 

 olivaceoalbus (Kuehner, 1926) and Gomphidius, they appear to arise 

 endogenously beneath an evanescent veil which extends from the edge 

 of the pileus to the stipe. 



The basidia show some primitive characters in their development. 

 Thus in Hygrophorus (Limacium) agathosmus (as in Neurophyllum 

 clavatum, p. 442), there are three divisions of the diploid nucleus although 

 only four (occasionally only two) basidiospores are formed (Maire, 1902). 

 The other nuclei remain in the basidium and perhaps are used in 

 the formation of a second spore generation. A very peculiar cytological 

 relationship was found in H. (Hygrocybe) conicus (Godfrinia conica) and 

 H. (Hygrocybe) Langei in which the cells of the mycelium and fructifi- 

 cation are bi- and multinucleate, while the cells of the hymenium and 

 subhymenium only contain one nucleus each (Maire, 1902; Fries, 1911; 

 Kuehner, 1926). The primary basidial nucleus divides only once (occa- 

 sionally twice in H. Langei), both daughter nuclei lie directly under 

 the top and gradually migrate into the middle of the basidium. Here- 

 upon two sterigmata are formed, each of which cuts off a large reniform 

 spore. Before or during the migration into the spores, both daughter 

 nuclei again divide so that at separation, the spores are binucleate. 

 While the two nuclei were seen lying close together in pairs in the trama, 

 fusion was not observed, although the hymenial nuclei are much larger 

 than those of the trama. The significance of this relationship may be 

 more fully explained when the development of the primary basidial 

 nucleus is better known. In H. (Hygrocybe) nigrescens (Kuehner, 

 1926), very closely related to H. (Hygroajbe) conicus, the young basidia 

 are binucleate and the subsequent development is the usual one for this 



